20117721 has 8 divisors (see below), whose sum is σ = 28887040. Its totient is φ = 12380112.

The previous prime is 20117719. The next prime is 20117723. The reversal of 20117721 is 12771102.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (20117719) and next prime (20117723).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20117721 - 2¹ = 20117719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20117723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 257881 + ... + 257958.

It is an arithmetic number, because the mean of its divisors is an integer number (3610880).

Almost surely, 2^20117721 is an apocalyptic number.

It is an amenable number.

20117721 is a deficient number, since it is larger than the sum of its proper divisors (8769319).

20117721 is a wasteful number, since it uses less digits than its factorization.

20117721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 515855.

The product of its (nonzero) digits is 196, while the sum is 21.

The square root of 20117721 is about 4485.2782522381. The cubic root of 20117721 is about 271.9732934058.

Adding to 20117721 its reverse (12771102), we get a palindrome (32888823).

The spelling of 20117721 in words is "twenty million, one hundred seventeen thousand, seven hundred twenty-one".